What's legal ?

[09.0]

Dutch twin shock is in with your theory then Nathan. Can't have it both ways which is my point. No means no. Anything else is Dutch twin shock.

[Nathan S]

Dutch twin shock is in with your theory then Nathan

Not really, Brad.

The Dutch bikes fail the "Could it have been built back in the day?" test - You couldn't build a CR480RZ in 1979/80, for example.
If Evo was an era (rather than a technological cut-off) then they would also fail the "Do they have an advantage over the 19xx model bikes?" test.

NB: I'm not suggesting those questions become the rules, just that the rules should reflect that intent.

Can't have it both ways which is my point.

Absolutely. We specifically want there to be a clear and fair cut off. The question is how to achieve that.

To tweak Iain's hypothetical example, you could build a MX250/360/500B in 1974, out of MX/SC-A and YZ-B parts. If anyone was prepared to butcher two vintage bikes, they could do it (and for less money than a complete YZ-B, so it's not an entirely stupid idea). It would be 100% legal for pre-75, despite the obvious Dutchness of it all.

OR, you could end up with a damn-near identical result by just using a stock MX-B chassis with the shock travel limited, and not butcher any bike. Yet this would be illegal?!

Neither option is perfect, neither is complete nonsense - the challenge is to work through the contradictions...

[Brian Watson]

Nathan....you couldn't have built a MX250/400B in 1974...because the 400 didn't exist....until 1975...remember model/year is the specific..not the date manufactured

[Nathan S]

Ah, yeah - I started off talking about the 250 specifically, then changed it to include the 400 (to make it closer to Iain's original post), but forgot about the 360 to 400... 

Earlier post edited to make it right...

[Freakshow]

All makes sence to me.....

[09.0]

  Neither option is perfect, neither is complete nonsense - the challenge is to work through the contradictions...     

why? The rules are clear enough as they are. The same old same old trying to bend the rules to fit my bike into a class.
Your own argument fell into a heap as you couldn't have done it back on the day. Iain's bike if it were ridden in pre 75 would open flood gates to others with 75 models retro fitting their bikes to 'comply'. Not to mention taking bikes away from pre 78. Again if he said I'm old slow and want to ride this bike in pre 78 then he would have gotten the thumbs up. I'd like Iain to say why he doesn't want to run it in pre 78.

[Nathan S]

Your own argument fell into a heap as you couldn't have done it back on the day.

Only because I originally, mistakenly included the 400. If we were talking about a 250, 360 or 500 then my point stands perfectly.

Iain's bike if it were ridden in pre 75 would open flood gates to others with 75 models retro fitting their bikes to 'comply'.

Who's to say that there aren't already plenty of neatly converted 1975 models running in pre-75?
More importantly, what makes a bike a particular model? It's the total sum of the important parts, not any one or two particular part(s) - in the cases we're talking about, a bike that is converted back is a bike that is legal.

Not to mention taking bikes away from pre 78.

How often do you see 1975 models in pre-78? In all of the club meets I've been to, and the few Nationals, I can recall seeing only a tiny number of 1975 models competing in pre-78 - a 75 CZ125 (once), my YZ125C (occasionaly), Graeme's RM-M (semi-regularly) and a couple of MX-Bs (semi-regularly). I'm sure there's more, but even so, it's a bloody short list...
I love the pre-78 class, but because it is a transition era, the difference in performance (most 1975 models to most 1977 models) is big.

I'd like Iain to say why he doesn't want to run it in pre 78.

I don't dare pretend to speak for Iain, but I can think of a few reasons why:
It will be far less competitive in pre-78;
It arguably it at home in pre-75;
The rules imply that it is not legal for pre-78 (due to the pre-75 motor);
He already has a "proper" pre-78 bike.

You've drawn your line in the sand, as is entirely your right. But until you can resolve the conflicts, then these sort of questions will continue to come up and continue to irritate you.

Let's say I had a V75, and neatly converted it back to VR250* specs (or TM250 or...).
For all intents and purposes, the bike is a 1974 model, and is 100% legal for pre-75, right?
If you agree, then explain how Iain's proposed by is not legal...
If you disagree, then explain how it could be illegal while the newly built frames are legal? Not to mention the impossibility of enforcing it...

*Bigk sold such a bike a couple of years back. Plus the work Montynut did in converting his LTR-modified VR250 back to pre-75 specs shows that it is entirely possible.

[worms]

if you take a 1975 model bike and convert it to a 74 model, it's still made in 1975, youve just butchered a bike for your own gains or losses. just ride the thing in pre78. And at your age Ian, you should know better

[Rossvickicampbell]

slightly off topic - Nathan why cannot a pre75 motor run in pre 78?

[Montynut]

Let's say I had a V75, and neatly converted it back to VR250* specs (or TM250 or...).
For all intents and purposes, the bike is a 1974 model, and is 100% legal for pre-75, right?
If you agree, then explain how Iain's proposed by is not legal...
If you disagree, then explain how it could be illegal while the newly built frames are legal? Not to mention the impossibility of enforcing it...

*Bigk sold such a bike a couple of years back. Plus the work Montynut did in converting his LTR-modified VR250 back to pre-75 specs shows that it is entirely possible.

Geeze Nathan don't bring me into this all I did was return a Pre75 frame to it's original state. By the way there are many differences between a VR250 frame and a V75 frame which I would think would render the V75 frame outside the rules although the engines are the same.

[maico police]

By the way there are many differences between a VR250 frame and a V75 frame which I would think would render the V75 frame outside the rules although the engines are identical but exhaust is not

I was told once that if I moved the shock mounts on my V75 back I'd have no trouble getting it into Pre 75. I couldn't bring myself to do it and I'm glad I didn't. It would have been butchery of a beautiful little bike.

[Montynut]

I would believe that you could run a V75 or even VA model in Pre75 with the rear sub frame modified at most Club events. The differences in the rear sub frame would rule it not eligible for Pre75 if properly examined.

[firko]

slightly off topic - Nathan why cannot a pre75 motor run in pre 78?

Ross...In my opinion a pre 75 engine can most definitely be used in pre '78 if, for whatever reason, the rest of the bike doesn't qualify for pre 75. For instance, if I fitted AW forks and longer, laid down shocks to my '74 Maico it'd automatically go into the pre '78 class. Ditto Iain's hypothetical '74 SC500 because it's been fitted with a '75 MX250-B frame. I don't know what all of the kerfuffle is about, it's all pretty simple if you sit down and think about it for a minute or two .

[IT400C]

Bracket Creep.....

So, if an MX400B frame is made legal in Pre-75 as long as it has an MX360 or SC500 motor, does that mean I could put the same motor in my IT400C (76 model), or YZ400C (76 model), restrict the suspension slightly, and run it in Pre 75?

Apart from one extra mounting point for the muffler, and one digit in the frame numbers, the YZ400C and IT400C frames are identical to the MX400B... (MXB: 510-0*****, YZC: 510-1*****, ITC: 510-2*****)

Bracket Creep...

[DJRacing]

slightly off topic - Nathan why cannot a pre75 motor run in pre 78?

Ross...In my opinion a pre 75 engine can most definitely be used in pre '78 if, for whatever reason, the rest of the bike doesn't qualify for pre 75. For instance, if I fitted AW forks and longer, laid down shocks to my '74 Maico it'd automatically go into the pre '78 class. Ditto Iain's hypothetical '74 SC500 because it's been fitted with a '75 MX250-B frame. I don't know what all of the kerfuffle is about, it's all pretty simple if you sit down and think about it for a minute or two .

18.5.5.1 Acceptable for the pre 78 classes are machines and components that are limited to the 1975, 1976, 1977 models alone. The only exception to this rule is where the model remains unaltered after this date.

That is what is quoted for pre78 rule number 1 for the year 2012
Take it as you want to read it, but it certainly doesn't include any parts from pre75??